1. Field of the Invention
The present invention relates to a deformable intraocular implantable refractive lens to correct vision problems, which lens is inserted into the eye anterior to the natural lens and has a functional design which minimizes cutting or stretching of the cornea to do so. The lens of the present invention may be multifocal to treat presbyopia.
2. Description of the Related Art
Doctors trained in ophthalmology routinely surgically extract cataract-impaired lenses from patients"" eyes and subsequently implant artificial lenses to prevent blindness. The artificial lens is typically manufactured from polymethylmethacrylate (PMMA), an acrylic plastic. PMMA is a preferred material because it is biologically compatible with the tissue of the eye, and it does not degrade over time.
Over the last 50 years, the success rate for implanting these intraocular lenses has improved to the point that surgeons now want to implant intraocular implantable refractive lenses anterior to the natural lenses to correct common vision problems, such as myopia (near-sightedness), hypermetropia (far-sightedness), and astigmatism (aberration in the convexity of the optic lens or cornea). In order to insert an intraocular lens, an incision of approximately 10 mm is made through the cornea or sclera. The new lens is passed through the incision into the anterior chamber of the eye. The inserted lens is then positioned over the pupil and anchored either anteriorly to or posteriorly from the iris. Unfortunately, the making of the incision has been known to cause astigmatism of the cornea.
Experience from cataract surgeries shows that the astigmatism will be reduced if a smaller incision is made. It follows that if the lens could be manipulated through a smaller incision, it will reduce the severity of the astigmatism. The optical portion of the intraocular lens, though, must have a diameter of at least approximately 6 mm in order to properly cover the pupil. So, the only way to pass a lens through a smaller incision is to first fold the lens into a u-shape or roll it so that the opposite edges are overlapping. However, currently designed PMMA lenses are rigid and too brittle to be rolled or folded. While it is known that a material which is rigid at a given thickness may be flexible at a lesser thickness, the maximum material thickness under which PMMA is flexible is approximately 0.25 mm. This thickness is too thin for use in a conventional implantable refractive lens because of the lens"" optics requirements.
A lens has a convex lenticular surface into which incident light passes. The lens also has a posterior surface, opposite the lenticular surface, from which the refracted light exits. The posterior surface may be convex, planar or concave. The power of the lens is determined by the curvature of the lenticular and posterior surfaces. Because the optical portion of the implantable refractive lens is approximately 6 mm wide and the thickest portion is at the center of the lens, a conventional lens having a maximum thickness of under 0.25 mm at its center in order to be rolled may possess the requisite curvature to be optically useful.
Alternative lens materials are also currently used for the replacements of the natural lenses of cataract patients. One such alternative lens material is an acrylic that has a lower molecular weight than PMMA. This lower-weight acrylic lens is softer than PMMA so it can be folded in a u-shape. However, if not handled very carefully, the lower-weight acrylic will crease, rendering it unusable. In addition, the material is soft enough to adhere to itself if it is rolled or folded far enough to allow overlapping. The multifocal lens of the present invention can be inserted xe2x80x9cflatxe2x80x9d (i.e., not folded) if the lens is too thick to be folded.
Another alternative lens material is silicone, the same material that is sometimes used in breast implants. The silicone collects protein in some patients, giving a yellow appearance and reducing the passage of light. The protein can become so dense as to create the appearance of a secondary cataract, significantly reducing the patient""s ability to see. This is usually a lesser concern for cataract patient, when compared to the blindness, which would result from the cataract. Also, most cataract patients tend to be elderly so the protein build-up might not advance too far during their lifetimes. For some cataract patients, though, the protein build-up necessitates that the silicone lens be removed and replaced. Because of the problems associated with protein build-up, silicone is preferably not used to make long-term intraocular implantable refractive lenses for implantation into younger persons.
Two inventions for a deformable intraocular lens are set forth in U.S. Pat. No. 4,573,998 issued March 1986, to Mazzocco; and U.S. Pat. No. 5,522,890 issued June 1996, to Nakajima et al. These inventions employ a lens made of a molded elastic material. They do not disclose or suggest the use of PMMA.
Other inventions generally related to the art of optical lenses include: U.S. Pat. No. 4,254,509 issued March 1981, to Tennant (Accommodating Intraocular a Implant); U.S. Pat. No. 4,585,456 issued April 1986, to Blackmore (Corrective Lens For The Natural Lens Of The Eye); U.S. Pat. No. 4,655,775 issued April 1987, to Clasby (Intraocular Lens With Ridges); U.S. Pat. No. 4,769,035 issued September 1988, to Kelman (Artificial Lens And The Method For Implanting Such Lens); U.S. Pat. No. 4,795,462 issued January 1989, to Grendahl (Cylindrically Segmented Zone Of Focus Artificial Lens); U.S. Pat. No. 4,816,032 issued March 1989, to Hetland (Arrangement In An Intraocular Anterior Chamber Lens); U.S. Pat. No. 4,950,290 issued August 1990, to Kamerling (Posterior Chamber Intraocular Lens); U.S. Pat. No. 4,994,080 issued February 1991, to Shepard (Optical Lens Having At Least One Stenopaeic Opening Located In The Central Area Thereof); U.S. Pat. No. 5,076,684 issued December 1991, to Simpson et al. (Multi-Focal Diffractive Ophthalmic Lenses); U.S. Pat. No. 5,098,444 issued March 1992, to Feaster (Epiphakic Intraocular Lens And Process Of Implantation); U.S. Pat. No. 5,166,711 issued November 1992, to Portney (Multifocal Ophthalmic Lens); U.S. Pat. No. 5,229,797 issued July 1993, to Futhey et al. (Multifocal Diffractive Ophthalmic Lenses); U.S. Pat. No. 5,258,025 issued November 1993, to Fedorov et al. (Corrective Intraocular Lens); U.S. Pat. No. 5,480,428 issued January 1996, to Fedorov et al. (Corrective Intraocular Lens). None of these inventions solves the above-disclosed problems associated with currently known deformable intraocular lenses.
Regarding multifocal lens, U.S. Pat. No. 5,800,532 to Lieberman discloses an intraocular lens that has a central portion having a first refractive power region and a peripheral portion having a second refractive power region. The second refractive power region is substantially concentrated only in one predetermined location; or is asymmetrically disposed on the inferior nasal quadrant of the intraocular lens.
U.S. Pat. Nos. 5,782,911 and 5,855,605 to Herrick disclose a multifocal lens system that includes a first optical lens having a predetermined diopter power and a second lens having a predetermined diopter power positioned eccentrically inferior of the first lens for receiving light rays from a distant object.
U.S. Pat. No. 5,628,794 to Lindstrom discloses a corneal implant lens which provides multifocal capability for the correction of presbyopia and ametropia and is coated with a hydrogel material.
U.S. Pat. No. 6,090,141 discloses an intracorneal lens that is inserted between the stromal layer of a cornea of an eye, and provides two regions of focality.
U.S. Pat. No. 5,682,223 to Menezes et al. discloses a multifocal annular ring lens comprising a central area with a circular disc, a plurality of annular rings having alternating spherical powers.
U.S. Pat No. 5,919,229 to Portney discloses a multifocal opthalmic lens having outer annular zones with vision correction powers less than a far vision correction power of the patient.
U.S. Pat. No. 6,120,148 to Fiala et al. discloses muiltifocal diffractive lens with a stepped design. The lens comprises at least two annular zones
A need exists for a deformable intraocular implantable refractive lens which requires a minimal incision through the cornea, but does not possess the drawbacks associated with the currently known, alternative lens materials.
Furthermore, a need exists for a multifocal lens that allows for the treatment of presbyopia and other conditions. Presbyopia is a condition, typically of middle age, where the lens of the eye reduces or eliminates accommodation and ability to focus on near objects. The lens of the present invention allows for treatment of presbyopia and provides a multifocal lens.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe such a lens as is achieved by the instant invention as claimed.
An object of the present invention is to provide an intraocular corrective lens, comprising an optical portion having a normal shape constructed of a material which is biologically compatible with the natural lens of the eye and for positioning anterior thereof. The optical portion may also have an anterior convex lenticular surface and a posterior surface, wherein the posterior surface comprises a central disk which is radially surrounded by a series of annular rings, forming a series of radial steps along said posterior surface; wherein said posterior surface and said anterior lenticular surface have a minimum separation of about 0.025 mm and a maximum separation of about 0.1 mm. The central disk may be of one diopter power and at least one annular ring is of a second diopter power. Finally, the lens of the present invention further comprises at least one anchor (i.e., haptics) attached to said optical portion for anchoring said optical portion anteriorly to the natural lens of the eye.
In another embodiment of the present invention, the optical portion of the corrective lens has a predetermined maximum thickness under which the material may be rolled without exceeding the elastic limit of the material, and a predetermined minimum thickness above which the material retains said normal shape. Therefore, the deformable intraocular corrective lens of this embodiment may be deformed for passage through a corneal incision having a length smaller than the diameter of the deformable intraocular corrective lens.
Preferably, the material forming said optical portion is polymethylmethacrylate (PMMA). Furthermore, the intraocular corrective lens of the present invention may optionally further comprise a transition area or stem disposed at the periphery of the optical portion, the anchor extending from the transition area. The transition area acts to support the haptics. Preferably, the haptic fingers extend from the transition area and sweep around the periphery the optical portion of the lens.
Preferably, the central disk is of one substantially constant diopter power and each annular ring is of a substantially constant diopter power. Preferably, the central disk is surrounded by 4 annular rings.
The present invention further relates to a deformable intraocular corrective lens, comprising:
a. an optical portion having a normal shape constructed of a material which is biologically compatible with the natural lens of the eye and for positioning anterior thereof, said optical portion having a predetermined maximum thickness of 0.25 mm under which the material may be rolled without exceeding the elastic limit of the material, said optical portion having a predetermined minimum thickness of 0.0125 mm above which the material retains said normal shape, whereby said deformable intraocular corrective lens is deformed for passage through a corneal incision having a length smaller than the diameter of the deformable intraocular corrective lens;
b. said optical portion also having an anterior convex surface and a posterior surface, wherein said posterior surface comprises a central disk which is radially surrounded by a series of annular rings, said central disk and said series of annual rings forming a series of radial steps along said posterior surface; whereby said posterior surface and said anterior lenticular surface having a maximum separation of 0.1 mm, and the central disk being of a first substantially constant diopter power and at least one annular ring is of a second substantially constant diopter power; and
c. and anchor anchoring said optical portion anteriorly to the natural lens of the eye.
The present invention further relates to an intraocular corrective lens, comprising: an optical portion having a normal shape constructed of a material which is biologically compatible with the natural shape of the eye that includes a central optic radially surrounded by at least one annular ring, radial steps defining said annular rings; and a pair of haptic fingers to anchor the optical portion in a eye.
Finally, the present invention relates to a method of correcting a cause of impaired vision, comprising the steps of:
a. making an incision for access to the anterior chamber of an eye having a length of about 4 mm or less;
b. providing a corrective lens formed of polymethylmethacrylate material having a thickness of about 0.25 mm or less, having a diameter of 6 mm., said optical portion also having an anterior convex surface and a posterior surface, wherein said posterior surface comprises a central disk which is radially surrounded by a series of annular rings, said central disk and said series of annual rings forming a series of radial steps along said posterior surface; whereby said posterior surface and said anterior lenticular surface having a maximum separation of 0.1 mm, and the central disk being of a first diopter power and at least one annular ring is of a second diopter power
c. integrally providing support haptics for anchoring the corrective lens;
d. rolling the corrective lens and the support haptics without exceeding the elastic limit of the polymethylmethacrylate material into a rolled package;
e. inserting the rolled package into the anterior chamber of the eye via the incision;
f. unrolling the rolled package internally of the anterior chamber;
g. anchoring the haptics anteriorly of the lens of the eye in the anterior chamber;
h. repairing the incision made in the eye.